Lubricating oil additive, lubricating oil, grease composition, fuel oil additive, fuel oil, and oil sludge suppression method

ABSTRACT

To provide a lubricating oil additive, a lubricating oil, a grease composition, a fuel oil additive, a fuel oil, and an oil sludge suppression method, which are capable of effectively suppressing oil sludge in the lubricating oil. The lubricating oil additive for suppressing oil sludge contains titanium dioxide particles as an active ingredient.

RELATED APPLICATIONS

The present application is a national phase of International Application Number PCT/JP2017/014381, filed Apr. 6, 2017, which claims priority to Japanese Application Number 2016-245194, filed Dec. 19, 2016.

TECHNICAL FIELD

The present invention relates to a lubricating oil additive, a lubricating oil, a grease composition, a fuel oil additive, a fuel oil, and an oil sludge suppression method.

BACKGROUND ART

There has hitherto been known a lubricating oil in which titanium dioxide is contained to reduce the friction coefficient of the lubricating oil (see, e.g., Patent Document 1).

CITATION LIST Patent Documents

Patent Document 1: Japanese Patent Laid-Open Publication No. 2009-179715

SUMMARY OF INVENTION Technical Problem

Addition of titanium dioxide to the lubricating oil in the related art has been intended to make the titanium dioxide act to polish asperities of a metal surface or infiltrate into the asperities of the metal surface, thereby improving roughness of the metal surface and reducing the friction coefficient of the lubricating oil, focusing on the particle size and the hardness of titanium dioxide.

A point that oil sludge in the lubricating oil is suppressed by adding titanium dioxide to the lubricating oil has not been known.

An object of the present invention is to provide a lubricating oil additive, a lubricating oil, a grease composition, a fuel oil additive, a fuel oil, and an oil sludge suppression method, which are capable of effectively suppressing oil sludge in the lubricating oil.

Solution to Problem

The present invention has been accomplished by focusing attention on the photocatalytic function of titanium dioxide particles, and by finding that addition of the titanium dioxide particles as an active ingredient to the lubricating oil develops a useful effect of suppressing the oil sludge in the lubricating oil.

The present invention provides a lubricating oil additive defined in each of the following (1) to (8).

(1) A lubricating oil additive for suppressing an increase of oil sludge, wherein the lubricating oil additive contains, as an active ingredient, titanium dioxide particles on which coating treatment is not carried out, the titanium dioxide particles being added in amount of 0.005 wt % or more and less than 0.3 wt % to a lubricating oil.

(2) The lubricating oil additive defined in (1), wherein the titanium dioxide particles are anatase type titanium dioxide particles.

(3) The lubricating oil additive defined in (1) or (2), wherein the titanium dioxide particles are nanoparticles having an average particle size of 1 nm to 300 nm.

(4) The lubricating oil additive defined in any one of (1) to (3), wherein the titanium dioxide particles have the photocatalytic function.

(5) The lubricating oil additive defined in any one of (1) to (4), further containing oil.

(6) The lubricating oil additive defined in any one of (1) to (5), wherein the lubricating oil additive is given as a composition mixed with oil and containing 0.1 to 5 wt % of the titanium dioxide particles.

(7) The lubricating oil additive defined in any one of (1) to (6), wherein the lubricating oil additive is effective in additionally improving fuel consumption.

(8) The lubricating oil additive defined in any one of (1) to (7), wherein the lubricating oil additive is effective in additionally suppressing mechanical vibration.

Furthermore, the present invention provides a lubricating oil defined in the following (9) or (10).

(9) A lubricating oil into which the lubricating oil additive defined in any one of (1) to (8) is mixed.

(10) The lubricating oil defined in (9), wherein the lubricating oil contains 0.01 to 0.1 wt % of the titanium dioxide particles.

Still further, the present invention provides a grease composition defined in the following (11).

(11) A grease composition into which the lubricating oil defined in (9) or (10) is mixed.

Still further, the present invention provides an oil sludge suppression method defined in each of the following (12) to (15).

(12) An oil sludge suppression method of suppressing oil sludge by adding the lubricating oil additive defined in any one of (1) to (8) to a lubricating oil.

(13) The oil sludge suppression method defined in (12), the method ¥

(15) The oil sludge suppression method defined in any one of (12) to (14), the method using a lubricating oil to which 0.005 wt % or more and less than 0.3 wt % of titanium dioxide particles are added.

Still further, the present invention provides a fuel oil additive defined in each of the following (16) to (23).

(16) A fuel oil additive for suppressing oil sludge, wherein the fuel oil additive contains, as an active ingredient, titanium dioxide particles on which coating treatment is not carried out.

(17) The fuel oil additive defined in (16), wherein the fuel oil additive is used in a state of adding 0.00001 wt % or more and less than 0.01 wt % of the titanium dioxide particles to a fuel oil.

(18) The fuel oil additive defined in (16) or (17), wherein the titanium dioxide particles are anatase type titanium dioxide particles.

(19) The fuel oil additive defined in any one of (16) to (18), wherein the titanium dioxide particles are nanoparticles having an average particle size of 1 nm to 300 nm.

(20) The fuel oil additive defined in any one of (16) to (19), wherein the fuel oil additive is given as a composition containing another liquid fuel oil additive.

(21) The fuel oil additive defined in any one of (16) to (20), wherein the fuel oil additive is effective in additionally improving fuel consumption.

(22) The fuel oil additive defined in any one of (16) to (21), wherein the fuel oil additive is effective in additionally reducing emissions of acid gases.

(23) The fuel oil additive defined in any one of (16) to (22), wherein the fuel oil additive is effective in additionally promoting combustion of the fuel oil, cleaning a combustion chamber, or dispersing the oil sludge.

Still further, the present invention provides a fuel oil defined in the following (24).

(24) A fuel oil to which the fuel oil additive defined in any one of (16) to (23) is added.

Still further, the present invention provides an oil sludge suppression method defined in each of the following (25) to (28).

(25) An oil sludge suppression method of suppressing oil sludge by adding the fuel oil additive defined in any one of (16) to (23) to a fuel oil.

(26) The oil sludge suppression method defined in (25), the method being effective in additionally improving fuel consumption.

(27) The oil sludge suppression method defined in (25) or (26), the method being effective in additionally reducing emissions of acid gases.

(28) The oil sludge suppression method defined in any one of (25) to (27), the method being effective in additionally promoting combustion of the fuel oil, cleaning a combustion chamber, or dispersing the oil sludge.

Advantageous Effects of Invention

The present invention can provide the lubricating oil additive, the lubricating oil, the grease composition, the fuel oil additive, the fuel oil, and the oil sludge suppression method, which are capable of effectively suppressing the oil sludge by utilizing the photocatalytic function of the titanium dioxide particles. Furthermore, the present invention can provide the lubricating oil additive, the lubricating oil, the grease composition, the fuel oil additive, the fuel oil, and the oil sludge suppression method, which are capable of, in addition to effectively suppressing the oil sludge, improving fuel consumption and/or suppressing mechanical vibration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting changes of friction coefficient in wear tests using a lubricating oil (i.e., an additive lubricating oil A) to which a lubricating oil additive according to the embodiment is added and which contains 0.3% by weight (wt %) of titanium dioxide particles, a lubricating oil (i.e., an additive lubricating oil B) to which the lubricating oil additive according to the embodiment is added and which contains 0.03 wt % of the titanium dioxide particles, and an lubricating oil to which the lubricating oil additive according to the embodiment is not added.

FIG. 2 is a graph depicting the changes of the friction coefficient in a period of 10 minutes after the start in the results of the wear tests depicted in FIG. 1.

FIG. 3 is a graph depicting the changes of the friction coefficient in a period of 10 minutes before the end in the results of the wear tests depicted in FIG. 1.

FIG. 4 is a graph depicting changes of oil temperature in the wear tests depicted in FIG. 1.

FIG. 5 is a graph depicting the changes of the oil temperature in a period of 10 minutes before the end in the changes of the oil temperature depicted in FIG. 4.

FIGS. 6A and 6B represent wear loss weights in the wear tests depicted in FIG. 1.

FIGS. 7A and 7B represent the results of running tests using the additive lubricating oil to which the lubricating oil additive according to the embodiment is added, and the lubricating oil to which the lubricating oil additive according to the embodiment is not added.

FIGS. 8A and 8B represent the results of vibration tests (vibration results in a width direction of a vehicle body) using the additive lubricating oil to which the lubricating oil additive according to the embodiment is added, and the lubricating oil to which the lubricating oil additive according to the embodiment is not added.

FIGS. 9A and 9B represent the results of vibration tests (vibration results in a longitudinal direction of the vehicle body) using the additive lubricating oil to which the lubricating oil additive according to the embodiment is added, and the additive-free lubricating oil to which the lubricating oil additive according to the embodiment is not added.

FIGS. 10A and 10B are graphs depicting the results of engine output tests using an additive fuel oil to which a fuel oil additive according to the embodiment is added, and an additive-free fuel oil to which the fuel oil additive according to the embodiment is not added.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below. A lubricating oil additive according to the embodiment is used in fashion added to lubricating oils for internal combustion engines, industrial equipment, precision equipment, mechanical equipment, etc. The lubricating oil added with the lubricating oil additive according to the embodiment can be used in fashion mixed to grease compositions for use in industrial equipment, precision equipment, mechanical equipment, etc. Application examples of the lubricating oil and the grease component according to the embodiments include engine oils for ships and vehicles, hydraulic oils for shock absorbers and hydraulic equipment, lubricating oils and greases for rotating equipment, bearings, and gears, though not limited to them.

(Lubricating Oil Additive)

The lubricating oil additive according to the embodiment contains titanium dioxide particles having the photocatalytic function. Those titanium dioxide particles can be given as titanium dioxide particles having the anatase type crystal structure. Because anatase type titanium dioxide is able to develop the photocatalytic function by the action of an ultraviolet ray such as sunlight, it is usually used under environments where the sunlight (ultraviolet ray) hits, for example, by forming a layer of the anatase type titanium dioxide on the surface of an article irradiated with the sunlight (ultraviolet ray). On the other hand, lubricating oils used inside internal combustion engines, industrial equipment, precision equipment, or mechanical equipment are usually present in dark places where the ultraviolet ray does not reach. For that reason, the lubricating oil additive containing the anatase type titanium dioxide has not been added to the lubricating oils used in those places in expectation of the photocatalytic function.

The lubricating oil additive according to the embodiment is an additive to be mixed into the lubricating oil that is used in the dark places where the sunlight (ultraviolet ray) does not reach. The inventor has found that, when the lubricating oil additive according to the embodiment is added to the lubricating oil used even in the dark places inside the internal combustion engines, the industrial equipment, the precision equipment, or the mechanical equipment, oil sludge in the lubricating oil is suppressed. Such a result is presumably attributable to the fact that plasma is generated with mechanical sliding and the anatase type titanium dioxide particles contained in the lubricating oil additive are caused to develop the photocatalytic function by the generated plasma (see Toshio Sakurai; “Physical Chemistry of Lubrication”, pp. 151-152, by Saiwai Shobo). Thus, it deems that the photocatalytic function of the titanium dioxide particles acts to suppress polymerization reaction and oxidation reaction of the lubricating oil and to decompose products produced by the polymerization reaction and the oxidation reaction, whereby an increase of the oil sludge in the lubricating oil can be suppressed.

Furthermore, the suppression of an increase of the oil sludge in the lubricating oil is contributable to giving the effects such as improving fuel consumption and suppressing mechanical vibration. When the oil sludge in the lubricating oil increases, it is known that, with the oil sludge coming into gaps between mechanical parts, friction force between the mechanical parts increases and the fuel consumption degrades. It is also known that an increase of the friction force between the mechanical parts with the presence of the oil sludge impedes smooth sliding between the mechanical parts (namely, causes the mechanical parts to swing from side to side) and generates mechanical vibration. In contrast, when the lubricating oil additive according to the embodiment is added to the lubricating oil, the oil sludge is suppressed and friction between the mechanical parts caused by the oil sludge is also suppressed. Therefore, the effects such as improving the fuel consumption and suppressing the mechanical vibration are further obtained.

The titanium dioxide particles in this embodiment are nanoparticles having an average particle size of 1 nm to 300 nm and more preferably 1 nm to 100 nm. By using the titanium dioxide particles in the form of nanoparticles, when the lubricating oil additive is added to the lubricating oil, the effect of making a metal surface (mechanical surface) closer to a mirror surface can be obtained in addition to the photocatalytic function because the titanium dioxide particles polish asperities of the metal surface and infiltrate into the asperities of the metal surface. As a result, an oil film ratio (i.e., oil film thickness (μm)/average surface roughness (μm)=Λ (lambda value)) of the metal surface is increased, and the friction between the mechanical parts can be suppressed.

Moreover, the lubricating oil additive according to the embodiment is in the powdery form and is superior in transportability and quality retention. A user can cause the lubricating oil additive to develop the function such as suppressing the oil sludge by, immediately before use, taking out a small amount (e.g., about 100 ml) of the target lubricating oil into a separate container, adding a required amount of the powdery lubricating oil additive to the taken-out lubricating oil, and mixing it into the target lubricating oil after stirring for 2 to 3 minutes.

In addition, coating treatment intended to, for example, promote dispersion and prevent precipitation is not carried out on the titanium dioxide particles in this embodiment. The reason resides in enabling the photocatalytic function of the titanium dioxide to be sufficiently developed. However, the titanium dioxide particles in this embodiment are nanoparticles and hence highly condensable, and they further exhibit higher precipitability because of having a higher specific gravity than the lubricating oil. In view of the above point, the lubricating oil additive according to the embodiment may contain a dispersant for improving dispersion of the titanium dioxide particles, and a precipitation inhibitor for suppressing precipitation of the titanium dioxide particles.

The dispersant added to the lubricating oil additive is adsorbed on surfaces of the titanium dioxide particles, thus effectively preventing cohesion between the titanium dioxide particles and improving dispersion of the titanium dioxide particles in the lubricating oil. The dispersant is not limited to particular one, and it may be suitable one of, for example, high-molecular dispersants such as polyester-based, polyurethane-based, polyamino-based, acrylic, styrene-acrylic, and styrene-maleic copolymer dispersants, and surfactant dispersants such as alkyl sulfonate-based, quaternary ammonium-based, higher-alcohol alkylene oxide-based, polyalcohol ester-based, and alkylpolyamine-based dispersants.

The precipitation inhibitor added to the lubricating oil additive can suppress the precipitation of the titanium dioxide particles by bringing the titanium dioxide particles, which are enveloped by the dispersant, into a state floating or suspended in the lubricating oil. The precipitation inhibitor is also not limited to particular one, and it may be, for example, amide, ethanol, isopropanol, butyl acetate, alkyl cyclohexane, or polyethylene oxide.

A usage method of the lubricating oil additive according to the embodiment will be described below. In this embodiment, the lubricating oil additive is added to the lubricating oil in such an amount that the concentration of the titanium dioxide particles in the lubricating oil is 0.005 wt % or more and less than 0.3 wt % (50 ppm or more and less than 3000 ppm at weight ratio). The reason is as follows. If the concentration of the titanium dioxide particles in the lubricating oil is less than 0.005 wt % (50 ppm), the photocatalytic effect of the titanium dioxide is not effectively developed. On the other hand, if the concentration of the titanium dioxide particles is 0.3 wt % (3000 ppm) or more, the abrasion effect of the titanium dioxide particles becomes too large, and a possibility of deteriorating machines is caused. In particular, the concentration of the titanium dioxide particles in the lubricating oil is preferably 0.01 to 0.1 wt % (100 to 1000 ppm at weight ratio) and more preferably 0.03 to 0.04 wt % (300 to 400 ppm at weight ratio). When the concentration of the titanium dioxide particles in the lubricating oil additive is 3 wt %, for example, the user can set the concentration of the titanium dioxide particles in the lubricating oil to 0.03 wt % (300 ppm) by adding 0.255 g of the lubricating oil additive to 1000 ml (850 g) of the lubricating oil with density of 0.85.

(Additive Composition)

Another embodiment of the lubricating oil additive according to the present invention is a liquid composition containing the above-described lubricating oil additive and oil. By preparing the lubricating oil additive as the liquid additive composition, the anatase type titanium dioxide particles can be more effectively dispersed into the lubricating oil than in the case of using the powdery lubricating oil additive when the additive composition is added to the lubricating oil. The oil used in the additive composition is not limited to particular one, and it may be a base oil used as the lubricating oil (e.g., an engine oil) into which the additive composition is added. Alternatively, part of the lubricating oil before being added with the additive composition may be given as the oil used in the additive composition. A mineral oil or a synthetic oil having dynamic viscosity of 5 to 100 mm²/s at 40° C. is preferably used as the oil used in the additive composition. The mineral oil may be, for example, a fraction of distillates of the lubricating oil, which are obtained from a paraffin-based crude oil, a naphthenic crude oil, an aromatic crude oil, etc. The synthetic oil may be, for example, a polyolefin synthetic oil such as polyalphaolefin, an ester synthetic oil such as diester, or alkyl naphthalene. In this embodiment, it is assumed that the G3 oil in accordance with SAE Base Oil Classifications is used as a base oil of the lubricating oil additive.

The additive composition according to this embodiment contains 0.1 to 5 wt % of the anatase type titanium dioxide particles. Similarly to the above-described powdery lubricating oil additive, when added to the lubricating oil, the additive composition according to this embodiment can be added in such an amount that the concentration of the titanium dioxide particles in the lubricating oil is 0.005 wt % or more and less than 0.3 wt % (50 ppm or more and less than 3000 ppm at weight ratio), more preferably 0.01 to 0.1 wt % (100 to 1000 ppm at weight ratio), and even more preferably 0.03 to 0.04 wt % (300 to 400 ppm at weight ratio).

For example, the additive composition in which the concentration of the titanium dioxide particles is about 1.18 wt % can be prepared by adding 1 g of the titanium dioxide particles to a container that contains 100 ml (85 g) of the oil with density of 0.85. In this case, the user can set the concentration of the anatase type titanium dioxide particles in the lubricating oil to about 0.03 wt % (about 300 ppm) by adding the additive composition (containing 1 g of the titanium dioxide particles) in an amount corresponding to the above-mentioned one container to 3500 ml (2975 g) of the lubricating oil with density of 0.85.

The additive composition according to this embodiment may contain 1 to 5% by volume (vol %) of the above-mentioned dispersant. Because the titanium dioxide particles in this embodiment are nanoparticles of 1 to 300 nm, they tend to cohere when added to prepare the additive composition containing the oil. Thus, by adding the dispersant to the additive composition, cohesion of the titanium dioxide particles can be effectively suppressed in not only the additive composition containing the oil, but also in the lubricating oil to which the additive composition has been added. Moreover, the titanium dioxide particles can be dispersed to the entirety of the lubricating oil. As a result, the photocatalytic function of the titanium dioxide particles can be sufficiently developed in the lubricating oil.

The additive composition according to this embodiment may contain 1 to 5 vol % of the above-mentioned precipitation inhibitor. Usually, the titanium dioxide particles have a comparatively high specific gravity and tend to precipitate. In this embodiment, by adding the precipitation inhibitor to the lubricating oil additive, the titanium dioxide particles can be prevented from precipitating not only in the additive composition containing the oil, but also in the lubricating oil to which the additive composition has been added. Thus, when the user adds the additive composition to the lubricating oil, the titanium dioxide particles in the additive composition can be added in a comparatively uniform concentration to the lubricating oil, and the titanium dioxide particles can be comparatively uniformly dispersed in the lubricating oil. Hence the photocatalytic function of the titanium dioxide particles can be more effectively developed.

(Lubricating Oil)

The lubricating oil according to the embodiment is a lubricating oil mixed with the above-described lubricating oil additive (including the above-described additive composition). The lubricating oil before being mixed with the lubricating oil additive is not limited to particular one, and it may be a lubricating oil that is popularly commercialized and used. In this embodiment, the lubricating oil additive is mixed into the lubricating oil in such an amount that the concentration of the titanium dioxide particles in the lubricating oil is 0.005 wt % or more and less than 0.3 wt % (50 ppm or more and less than 3000 ppm at weight ratio), more preferably 0.01 to 0.1 wt % (100 to 1000 ppm at weight ratio), and even more preferably 0.03 to 0.04 wt % (300 to 400 ppm at weight ratio). The lubricating oil mixed with the lubricating oil additive as described above can be used by injecting the lubricating oil into internal combustion engines, industrial equipment, precision equipment, mechanical equipment, etc.

(Grease Composition)

The grease composition according to the embodiment is a grease composition mixed with the above-described lubricating oil. Ingredients of the grease composition other than the lubricating oil are not limited to particular ones, and they may be ingredients that are popularly used. Since the grease composition according to the embodiment contains the lubricating oil containing the anatase type titanium dioxide particles, the grease composition can suppress, when applied to the industrial equipment, the precision equipment, the mechanical equipment, etc., oxidation of the lubricating oil in the grease composition with the photocatalytic function caused by plasma generated in such equipment. Accordingly, in addition to providing the above-described function of suppressing the oil sludge, the grease composition can maintain performance of retaining the lubricating oil for a longer period, and can prolong a service lifetime.

Example 1

(Wear Tests)

The following is an example of measuring friction coefficient μ of a lubricating oil (called an additive lubricating oil A hereinafter) to which the lubricating oil additive according to the embodiment is added and which contains 0.3% wt % (3000 ppm at weight ratio) of the titanium dioxide particles, a lubricating oil (called an additive lubricating oil B hereinafter) to which the lubricating oil additive according to the embodiment is added and which contains 0.03 wt % (300 ppm at weight ratio) of the titanium dioxide particles, and a lubricating oil (called an additive-free lubricating oil hereinafter) to which the lubricating oil additive according to the embodiment is not added. More specifically, the friction coefficient μ was measured by conducting a wear test for 60 minutes under conditions listed in the following Table 1 with a high-speed FALEX test machine of Pin-VeeBlock. An engine oil with the SAE viscosity grade of 0W-20 was used as the lubricating oil. Although the titanium dioxide particles were produced so as to have the average particle size of 30 nm in this Example, the particle size of the titanium dioxide particles had a variation with a peak at about 30 nm due to a production method for the titanium dioxide particles (this is similarly applied to other Examples described later). The additive lubricating oil B added with 0.03 wt % of the titanium dioxide particles is the lubricating oil obtained by mixing the lubricating oil additive according to the embodiment in conformity with the above-described usage method.

TABLE 1 Test Conditions Load (N) 1334 Speed (m/s) 0.4 Time (min) 60 Oil Temp. (° C.) Without Control Sample Material Pin SUJ-2 Mirror Surface Finish Hardness 60 (HRC) Block SCM421 Polishing Finish ″ 45 Engine Oil Toyota Castle OW-20SN

(Friction Coefficient)

FIG. 1 is a graph depicting changes of the friction coefficient μ in wear tests using the additive lubricating oils A and B and the additive-free lubricating oil. FIG. 2 is a graph depicting the changes of the friction coefficient μ in a period of 10 minutes after the start in the results of the wear tests depicted in FIG. 1, and FIG. 3 is a graph depicting the changes of the friction coefficient μ in a period of 10 minutes before the end in the results of the wear tests depicted in FIG. 1.

First, the friction coefficient μ for each of the lubricating oils in the period of 10 minutes after the start is described. As depicted in FIGS. 1 and 2, comparing the additive-free lubricating oil and the additive lubricating oil A containing 0.3 wt % of the titanium dioxide particles, the friction coefficient μ is lower in the period of 10 minutes after the start in the case of using the additive lubricating oil A than in the case of using the additive-free lubricating oil. Similarly, comparing the additive-free lubricating oil and the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles, the friction coefficient μ is lower in the period of 10 minutes after the start in the case of using the additive lubricating oil B than in the case of using the additive-free lubricating oil. Comparing the additive lubricating oil A containing 0.3 wt % of the titanium dioxide particles and the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles, the friction coefficient μ is lower in the period of 10 minutes after the start in the case of using the additive lubricating oil A than in the case of using the additive lubricating oil B. Those results are presumably attributable to the fact that, immediately after adding the titanium dioxide particles to the lubricating oil, wear of the metal surface is promoted and surface roughness of the friction surface is improved by the titanium dioxide particles, whereby a thicker oil film is formed on the metal surface and the friction coefficient μ is reduced.

Next, the friction coefficient μ for each of the lubricating oils in the period of 10 minutes before the end (i.e., during the period from 50 minutes to 60 minutes after the start) is described. As depicted in FIGS. 1 and 3, comparing the additive-free lubricating oil and the additive lubricating oil A containing 0.3 wt % of the titanium dioxide particles, the friction coefficient μ is higher in the period of 10 minutes before the end in the case of using the additive lubricating oil A than in the case of using the additive-free lubricating oil. On the other hand, comparing the additive-free lubricating oil and the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles, the friction coefficient μ is lower in the period of 10 minutes before the end in the case of using the additive lubricating oil B than in the case of using the additive-free lubricating oil. Such a result is presumably attributable to the fact that, in the case of using the additive lubricating oil B in which the concentration of the titanium dioxide particles is 0.03 wt %, the photocatalytic function of the anatase type titanium dioxide particles is developed and the oil sludge is suppressed with the lapse of a certain time after adding the titanium dioxide particles to the lubricating oil, whereby an increase of friction force caused by the oil sludge is suppressed and the friction coefficient μ is reduced in comparison with that in the case of using the additive-free lubricating oil. The fact that the photocatalytic function of the titanium dioxide particles is developed in the case of using the additive lubricating oil B can be deduced from later-described Examples 2 and 3 as well. Regarding the case of using the additive lubricating oil A containing 0.3 wt % of the titanium dioxide particles, it deems that, because the lubricating oil contains an excessive amount of the titanium dioxide particles, many of the titanium dioxide particles infiltrate into the friction surface and increase the friction force with the lapse of a certain time after adding the titanium dioxide particles to the lubricating oil, whereby the friction coefficient μ is increased in comparison with that in the case of using the additive-free lubricating oil.

(Oil Temperature)

Changes of oil temperature in the wear tests of the additive lubricating oils A and B and the additive-free lubricating oil will be described below with reference to FIGS. 4 and 5. FIG. 4 is a graph depicting the changes of the oil temperature in the wear tests of the additive lubricating oils A and B and the additive-free lubricating oil, and FIG. 5 is a graph depicting the changes of the oil temperature in a period of 10 minutes before the end in the changes of the oil temperature depicted in FIG. 4.

As depicted in FIGS. 4 and 5, the oil temperature rises from the start of the wear tests in all of the additive lubricating oils A and B and the additive-free lubricating oil. Then, the oil temperature hardly rises after reaching about 20 to 30 minutes from the test start. Regarding the additive-free lubricating oil and the additive lubricating oil A containing 0.3 wt % of the titanium dioxide particles, the oil temperature remains almost constant even after the lapse of 40 minutes from the test start. On the other hand, regarding the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles, the oil temperature begins to lower at about 40 minutes from the test start and, as depicted in FIG. 5, it is lower than that of the additive-free lubricating oil by about 20° C. after 60 minutes from the test start.

As described above, regarding the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles, a rise of the oil temperature can be suppressed in comparison with the additive-free lubricating oil particularly after the lapse of a certain time from the test start. Thus, the lubricating oil added with the lubricating oil additive according to the embodiment makes it possible to suppress the oxidation reaction and the polymerization reaction of the lubricating oil caused by the rise of the oil temperature, to suppress production of the oil sludge promoted by the oxidation reaction and the polymerization reaction, and to prolong the service lifetime of the lubricating oil. Furthermore, as known in the art, the rise of the oil temperature reduces viscosity of the lubricating oil, thus causing a decrease of the thickness of the oil film and an increase of the friction force. In the case of using the lubricating oil added with the lubricating oil additive according to the embodiment, since the rise of the oil temperature can be suppressed, it is also possible to suppress the above-mentioned increase of the friction force, which is caused by thinning of the oil film. The above point can be further confirmed from the above-described changes of the friction coefficient μ depicted in FIGS. 1 to 3.

(Wear Loss Weight)

A relation between each of the additive lubricating oils A and B and the additive-free lubricating oil and wear loss weights of metals will be described below with reference to FIGS. 6A and 6B. FIG. 6A is a table representing wear loss weights in the wear tests depicted in FIG. 1, and FIG. 6B is a bar graph representing the wear loss weights represented in FIG. 6A. In the wear tests conducted in this Example, a circular columnar metal (SUJ-2) called Pin was gripped in a sandwiched relation by a metal (SCM421) called Vee Block, Pin was rotated while both the metals were held in the above state, and wear loss weights (mg) of Pin and Vee Block were detected. In this Example, when the additive-free lubricating oil was used, the wear loss weights of Pin and Vee Block were 0.7 mg and 0.2 mg, respectively. When the additive lubricating oil A containing 0.3 wt % of the titanium dioxide particles was used, the wear loss weights of Pin and Vee Block were 0.4 mg and 0.1 mg, respectively. When the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles was used, the wear loss weights of Pin and Vee Block were 0.4 mg and 0.4 mg, respectively.

In the wear tests conducted in this Example, as indicated in above Table 1, the hardness (HRC) of Pin used in the tests is 60, and the hardness (HRC) of Vee Block is 45. Thus, the hardness of Pin is higher than that of Vee Block. As seen from FIGS. 6A and 6B, in the cases of using the additive-free lubricating oil and the additive lubricating oil A containing 0.3 wt % of the titanium dioxide particles, wear of Pin is about four times that of Vee Block. On the other hand, it is also seen that, in the case of using the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles, wears of Pin and Vee Block are substantially the same. It is further seen that the wear of Pin is reduced from 0.7 in the case of using the additive-free lubricating oil to 0.4 in the case of using the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles. From the above results, the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles can be regarded as effective in, when applied to abrasion between metals, reducing wear of one of the metals having higher hardness. Such an effect is expected to provide the following advantages.

In an engine valve, for example, a shim is pushed out with rotation of a cam nose having a substantially elliptic shape and a valve coupled to a shim is opened, whereupon a gasoline-gas mixture can be introduced to a combustion chamber. Thus, because the engine valve has a mechanism in which the cam nose is rotated while contacting the shim, abrasion occurs between the cam nose and the shim. If the cam nose is worn, the cam nose can no longer sufficiently push out the shim, and the engine valve cannot be sufficiently opened. Since the additive lubricating oil added with the lubricating oil additive according to the embodiment can suppress, when applied to abrasion between metals, wear of one of the metals having higher hardness, the wear of the cam nose having higher hardness can be reduced, and the service lifetime of the cam nose can be prolonged.

Example 2

(Infrared Spectroscopic Analysis)

Aiming to prove that the photocatalytic function of the titanium dioxide particles is developed in the lubricating oil when the lubricating oil additive according to the embodiment is added to the lubricating oil, the inventor conducted an infrared spectroscopic analysis (also called an FT-IR analysis hereinafter) on the lubricating oil to which the lubricating oil additive according to the embodiment is added. In this Example, regarding each of the additive-free lubricating oil before the lubricating oil additive according to the embodiment is added and the additive lubricating oil B containing 0.03 wt % of the titanium dioxide particles with addition of the lubricating oil additive according to the embodiment, the lubricating oil being sampled after running through a distance of 500 km, the FT-IR analysis was conducted by the liquid film method using a KBr Cell with a film thickness set to 0.1. It is known that an ester is produced by decomposition of oil sludge. In consideration of the above point, the inventor conducted the FT-IR analysis on the additive lubricating oil B containing 0.03 wt % of the anatase type titanium dioxide particles and the additive-free lubricating oil not containing the anatase type titanium dioxide particles, and detected an absorbance (transmittance) at a wavelength of 1730 cm⁻¹, which is absorbed by the ester (C═O). The following Table 2 indicates the result of the FT-IR analysis (i.e., the detected absorbance at the wavelength of 1730 cm⁻¹).

TABLE 2 Additive-Free Additive Lubricating Oil Lubricating Oil Absorbance(% T) 37.6245 39.1636

As seen from the above Table 2, the additive lubricating oil B containing 0.03 wt % of the anatase type titanium dioxide particles exhibits a higher absorbance at the wavelength of 1730 cm⁻¹ than the additive-free lubricating oil. This is presumably attributable to the fact that, in the additive lubricating oil B containing 0.03 wt % of the anatase type titanium dioxide particles, decomposition of the oil sludge is promoted by the photocatalytic function of the anatase type titanium dioxide particles in comparison with the additive-free lubricating oil and the ester (C═O) is produced. In this Example, the FT-IR analysis was conducted, as described above, using the additive-free lubricating oil and the additive lubricating oil B after being subjected to the wear test described in Example 1, namely after conducting the wear test for 60 minutes. When the wear test is conducted for a longer time than 60 minutes, it deems that the ester (C═O) in the additive lubricating oil B is detected at a higher absorbance because the oil sludge is further generated corresponding to the longer test time and is decomposed by the photocatalytic function.

Example 3

Furthermore, the inventor has found, from studies described below, that the photocatalytic function of the titanium dioxide particles is developed in the lubricating oil to which the lubricating oil additive according to the embodiment is added. In other words, it has been found that, when running a racing bike using an engine oil not added with the lubricating oil additive according to the embodiment, gasoline is mixed in the engine oil after the running. The result of conducting studies has shown the reason residing in that the gasoline leaks through a gap between a cylinder and a piston due to the oil sludge causing fixation of a piston ring which is to prevent mixing of the gasoline. In consideration of the above point, the inventor has conducted a test of running the racing bike in a similar manner after adding the lubricating oil additive according to the embodiment to the engine oil. As a result, it has been found that the oil sludge is suppressed and hence the mixing of the gasoline into the engine oil can be prevented. The suppression of the oil sludge in the above case cannot be explained as being resulted just from a decrease of the friction coefficient μ caused by the titanium dioxide particles, and it proves that the photocatalytic function has been developed by the anatase type titanium dioxide particles.

Example 4

(Running Tests)

Running tests using an engine oil to which the lubricating oil additive according to the embodiment is added (also called an additive engine oil hereinafter) and an engine oil to which the lubricating oil additive according to the embodiment is not added (also called an additive-free engine oil hereinafter) will be described below with reference to FIGS. 7A and 7B. FIGS. 7A and 7B depict the results of the running tests using the additive engine oil and the additive-free engine oil.

In this Example, the additive engine oil added with the lubricating oil additive according to the embodiment and containing 0.03 wt % (300 ppm at weight ratio) of the titanium dioxide particles and the additive-free engine oil not added with the lubricating oil additive according to the embodiment were each injected into the same vehicle, and the vehicle was driven to run twice on the same section (same highway section of about 100 Km) with each of those engine oils. Then, an average fuel consumption in the case of using the additive engine oil (i.e., an average of fuel amounts consumed for individual running times in two runs using the additive engine oil) and an average fuel consumption in the case of using the additive-free engine oil (i.e., an average of fuel amounts consumed for individual running times in two runs using the additive-free engine oil) were calculated.

FIG. 7A depicts the average fuel consumption in the case of using the additive engine oil and the average fuel consumption in the case of using the additive-free engine oil. As seen from FIG. 7A, the average fuel consumption is improved in the case of using the additive engine oil in comparison with the case of using the additive-free engine oil. The improvement of the fuel consumption is presumably resulted from the fact that, in the case of using the additive engine oil, the oil sludge is suppressed by the anatase type titanium dioxide particles and an increase of the friction force caused by the oil sludge is suppressed. More specifically, as depicted in FIG. 7B, the improvement of the fuel consumption ranging from about 5 to 10% during the vehicle running has been confirmed.

Example 5

(Vibration Tests)

Vibration tests using the additive engine oil and the additive-free engine oil will be described below with reference to FIGS. 8A to 9B. FIGS. 8A and 8B depicts the results of detecting vibration in a width direction of a vehicle body in the vibration tests using the additive engine oil and the additive-free engine oil. FIGS. 9A and 9B depict the results of detecting vibration in a longitudinal direction of the vehicle body in the vibration tests using the additive engine oil and the additive-free engine oil.

In this Example, the additive engine oil added with the lubricating oil additive according to the embodiment and containing 0.03 wt % (300 ppm at weight ratio) of the titanium dioxide particles and the additive-free engine oil not added with the lubricating oil additive according to the embodiment were each injected into the same vehicle. Then, a vibration meter was attached to an engine cover, and vibration in the width direction of a vehicle body (lateral acceleration) and vibration in the longitudinal direction of the vehicle body (longitudinal acceleration) were measured by operating an engine while the vehicle was kept stopped.

FIG. 8A depicts the result of detecting the vibration in the width direction of the vehicle body (lateral acceleration) in the case of using the additive-free engine oil, and FIG. 8B depicts the result of detecting the vibration in the width direction of the vehicle body (lateral acceleration) in the case of using the additive engine oil. As seen from FIGS. 8A and 8B, the vibration in the width direction of the vehicle body (lateral acceleration) is considerably suppressed in the case of using the additive engine oil in comparison with the case of using the additive-free engine oil. The vibration in the width direction of the vehicle body (lateral acceleration) can be regarded as vibration caused by head swings of an engine piston. Thus, it is thought that addition of the lubricating oil additive according to the embodiment to the engine oil has succeeded in suppressing mechanical vibration by reducing the friction force between a piston link and a cylinder, and by suppressing a stick slip phenomenon.

FIG. 9A depicts the result of detecting the vibration in the longitudinal direction of the vehicle body (longitudinal acceleration) in the case of using the additive-free engine oil, and FIG. 9B depicts the result of detecting the vibration in the longitudinal direction of the vehicle body (longitudinal acceleration) in the case of using the additive engine oil. As seen from FIGS. 9A and 9B, the vibration in the longitudinal direction of the vehicle body (longitudinal acceleration) has a vibration period T1 in the case of using the additive-free engine oil, but it has a vibration period T2, which longer than T1, in the case of using the additive engine oil. This is presumably attributable to the fact that addition of the lubricating oil additive according to the embodiment to the engine oil has moderated the vibration (change of amplitude) and has suppressed the mechanical vibration. In FIG. 9B, the period T1 is denoted by a dotted line for easier comparison between T1 and T2.

As described above, the lubricating oil additive according to the embodiment is an additive added to the lubricating oil that is used in the dark places where the sunlight (ultraviolet ray) does not reach, such as inside internal combustion engines, industrial equipment, precision equipment, or mechanical equipment, and it contains, as an active ingredient, the titanium dioxide particles having the photocatalytic function. By adding the lubricating oil additive according to the embodiment to the lubricating oil, the oil sludge can be suppressed by the photocatalytic function of the titanium dioxide particles even in the places inside the internal combustion engines, the industrial equipment, the precision equipment, or the mechanical equipment where the sunlight (ultraviolet ray) does not reach. In addition, with the suppression of the oil sludge, it is possible to suppress an increase of the friction coefficient μ caused by the oil sludge, and to develop the effects such as improving the fuel consumption and suppressing the mechanical vibration.

Furthermore, since coating treatment intended to, for example, promote dispersion and prevent precipitation is not carried out on the titanium dioxide particles in this embodiment, the photocatalytic function of the titanium dioxide particles can be sufficiently developed. Moreover, the titanium dioxide particles in this embodiment are nanoparticles with the average particle size of 1 nm to 300 nm and more preferably 1 nm to 100 nm. Accordingly, when the lubricating oil additive is added to the lubricating oil, the effect of making a metal surface closer to a mirror surface can be obtained in addition to the photocatalytic function because the titanium dioxide particles polish asperities of the metal surface and infiltrate into the asperities of the metal surface.

In this embodiment, the lubricating oil additive is mixed into the lubricating oil in such an amount that the concentration of the titanium dioxide particles in the lubricating oil is 0.005 wt % or more and less than 0.3 wt % (50 ppm or more and less than 3000 ppm at weight ratio), more preferably 0.01 to 0.1 wt % (100 to 1000 ppm at weight ratio), and even more preferably 0.03 to 0.04 wt % (300 to 400 ppm at weight ratio). As a result, the titanium dioxide particles can sufficiently develop the photocatalytic function, and drawbacks caused by an excessive amount of the titanium dioxide particles can be suppressed.

Subsequently, the fuel oil additive according to the embodiment is described. The fuel oil additive according to the embodiment can be used by adding the fuel oil additive to a fuel oil such as gasoline. The fuel oil additive according to the embodiment can be further applied to fuel oils such as kerosene, light oil, and heavy oil, in addition to gasoline. The fuel oil added with the fuel oil additive according to the embodiment can be used, for example, in vehicles, ships, airplanes, heaters, thermal power plants, etc.

(Fuel Oil Additive)

The fuel oil additive according to the embodiment contains titanium dioxide particles having the photocatalytic function. Those titanium dioxide particles can be given as titanium dioxide particles having the anatase type crystal structure. Although it is known, as described above, that the anatase type titanium dioxide particles develop the photocatalytic function by the action of an ultraviolet ray, the photocatalytic function by the action of the ultraviolet ray is not developed inside an internal combustion engine in which gasoline (fuel oil) is circulated, because the inside of the engine is a dark place where sunlight (ultraviolet ray) does not reach. However, the inventor has found that the fuel consumption is improved when the fuel oil additive according to the embodiment is added to the gasoline (fuel oil) burnt in the internal combustion engine. The inventor further has found that, when the fuel oil additive according to the embodiment is added to the fuel oil, combustion efficiency of the gasoline (fuel oil) is increased and emissions of acid gases in exhaust gas, such as carbon monoxide (CO), methane gas (CH₄), and nitrogen oxides (NO_(x)), are reduced. The improvement of the fuel consumption is presumably attributable to the fact that the anatase type titanium dioxide particles contained in the fuel oil additive function as a photocatalyst with the aid of a flame (light) generated by combustion (explosion) in the combustion chamber, and that oil sludge in the gasoline (fuel oil) is suppressed and decomposed. In particular, with the titanium dioxide functioning as the photocatalyst in the combustion chamber, it is possible not only to suppress polymerization reaction of the fuel oil and the oil sludge, but also to decompose the oil sludge by ions generated with the photocatalyst. Moreover, the titanium dioxide has the function capable of reducing the molecular weight of the fuel oil and promoting the combustion of the fuel oil. It is hence thought that complete combustion of the fuel oil can be promoted, emissions of the acid gases generated by incomplete combustion can be reduced, and that the fuel consumption can be improved.

The titanium dioxide particles in this embodiment are nanoparticles having the average particle size of 1 nm to 300 nm and more preferably 1 nm to 100 nm. By using the titanium dioxide particles in the form of nanoparticles, when the fuel oil additive is added to the fuel oil, the effect of making a metal surface (mechanical surface) closer to a mirror surface can be obtained in addition to the photocatalytic function because the titanium dioxide particles polish asperities of the metal surface and infiltrate into the asperities of the metal surface. As a result, the oil film ratio (i.e., oil film thickness (μm)/average surface roughness (μm)=Λ (lambda value)) in the metal surface is increased, and the friction between the mechanical parts can be suppressed.

The fuel oil additive according to the embodiment is in the powdery form and is superior in transportability and quality retention. The user can cause the fuel oil additive to develop the function such as suppressing the oil sludge in an internal combustion engine by, immediately before use, adding a required amount of the powdery fuel oil additive according to the embodiment to a liquid fuel oil additive different from the fuel oil additive according to the embodiment, e.g., the so-called water remover or detergent, and mixing it into target gasoline after stirring for 2 to 3 minutes.

Coating treatment intended to, for example, promote dispersion and prevent precipitation is not carried out on the titanium dioxide particles in this embodiment. The reason resides in enabling the photocatalytic function of the titanium dioxide to be sufficiently developed. Because the fuel oil additive according to the embodiment is added into an internal combustion engine, the added fuel oil additive is stirred and dispersed to some extent by operation of a piston and an engine shaft. However, the titanium dioxide particles in this embodiment are nanoparticles and hence highly condensable as in the above-described lubricating oil additive, and they further exhibit higher precipitability because of having a higher specific gravity than the fuel oil. In view of the above point, the fuel oil additive according to the embodiment may contain a dispersant for improving dispersion of the titanium dioxide particles, and a precipitation inhibitor for suppressing precipitation of the titanium dioxide particles.

The dispersant added to the fuel oil additive is adsorbed on surfaces of the titanium dioxide particles as in the above-described lubricating oil additive, thus effectively preventing cohesion between the titanium dioxide particles and improving dispersion of the titanium dioxide particles in the fuel oil. The dispersant is not limited to particular one, and it may be suitable one of, for example, high-molecular dispersants such as polyester-based, polyurethane-based, polyamino-based, acrylic, styrene-acrylic, and styrene-maleic copolymer dispersants, and surfactant dispersants such as alkyl sulfonate-based, quaternary ammonium-based, higher-alcohol alkylene oxide-based, polyalcohol ester-based, and alkylpolyamine-based dispersants.

The precipitation inhibitor added to the fuel oil additive can, as in the above-described lubricating oil additive, suppress the precipitation of the titanium dioxide particles by bringing the titanium dioxide particles, which are enveloped by the dispersant, into a state floated or suspended in the fuel oil. The precipitation inhibitor is also not limited to particular one, and it may be, for example, amide, ethanol, isopropanol, butyl acetate, alkyl cyclohexane, or polyethylene oxide.

Although the coating treatment is not carried out on the titanium dioxide particles in the fuel oil additive according to the embodiment, the titanium dioxide particles may be coated with organotitanium with intent to promote the precipitation inhibition effect and the dispersion effect.

A usage method of the fuel oil additive according to the embodiment will be described below. In this embodiment, the fuel oil additive is added to the fuel oil in such an amount that the concentration of the titanium dioxide particles in the fuel oil is 0.00001 wt % or more and less than 0.01 wt % (0.1 ppm or more and less than 100 ppm at weight ratio). The reason is as follows. If the concentration of the titanium dioxide particles in the fuel oil is less than 0.00001 wt % (0.1 ppm), the photocatalytic effect of the titanium dioxide is not effectively developed. On the other hand, if the concentration of the titanium dioxide particles is 0.01 wt % (100 ppm) or more, an amount of the precipitated titanium dioxide particles is increased, whereby the effect is relatively reduced with respect to the amount of the titanium dioxide particles and the cost is increased. The concentration of the titanium dioxide particles in the fuel oil is preferably 0.00001 to 0.01 wt % (0.1 to 100 ppm at weight ratio) and more preferably 0.0001 to 0.005 wt % (1 to 50 ppm at weight ratio). When the concentration of the titanium dioxide particles in the fuel oil additive is 3 wt %, for example, the user can set the concentration of the titanium dioxide particles in the fuel oil to 0.0031 wt % (31 ppm) by adding 35 g of the fuel oil additive to 45 L (33750 g) of the fuel oil with density of 0.75.

(Additive Composition)

Another embodiment of the fuel oil additive according to the present invention is a liquid composition containing the above-described fuel oil additive that contains the titanium dioxide, and a liquid fuel oil additive different from the fuel oil additive according to the embodiment, e.g., the so-called water remover or detergent. By preparing the fuel oil additive according to the embodiment as the liquid composition, the anatase type titanium dioxide particles can be more effectively dispersed into the fuel oil than in the case of using the powdery fuel oil additive directly in the powder form, when the additive composition is added to the fuel oil. The liquid fuel oil additive different from the fuel oil additive according to the embodiment may be, in addition to the so-called water remover and detergent, a deposit improver, an antiknock agent, an antioxidant, a metal activation agent, an antirust agent, an anticorrosive agent, a colorant, an odorant, an aromatic, an antistatic agent, a low-temperature fluidity improver, a cetane number improver, a lubrication improver, a discriminant agent, a defoamer, a deicing agent, an anti-smoking agent, a combustion improver, a sludge dispersant, etc., which can be added to the fuel oil.

The additive composition according to this embodiment contains 0.3 to 1.4 wt % of the anatase type titanium dioxide particles. Similarly to the above-described powdery lubricating oil additive, when added to the fuel oil, the additive composition according to this embodiment can be added in such an amount that the concentration of the titanium dioxide particles in the fuel oil is 0.00001 wt % or more and less than 0.01 wt % (0.1 ppm or more and less than 100 ppm at weight ratio) and more preferably 0.0001 to 0.005 wt % (1 to 50 ppm at weight ratio).

For example, the additive composition in which the concentration of the titanium dioxide particles is about 0.7 wt % can be prepared by adding the fuel oil additive containing 1 g of the titanium dioxide particles to a container that contains 360 ml (280.7 g) of the water remover having density of 0.78 and containing isopropyl alcohol as a main ingredient. In this case, the user can set the concentration of the anatase type titanium dioxide particles in the fuel oil to about 0.003 wt % (about 30 ppm) by adding the additive composition (containing 1 g of the titanium dioxide particles) in an amount corresponding to the above-mentioned one container to 45 L (33750 g) of the fuel oil with density of 0.75.

The additive composition according to this embodiment may contain 1 to 5 vol % of the above-mentioned dispersant. Because the titanium dioxide particles in this embodiment are nanoparticles of 1 to 300 nm, they tend to cohere when added to prepare the additive composition. Thus, by adding the dispersant to the additive composition, cohesion of the titanium dioxide particles can be effectively suppressed in not only the additive composition, but also in the fuel oil to which the additive composition has been added. Moreover, the titanium dioxide particles can be dispersed to the entirety of the fuel oil. As a result, the photocatalytic function of the titanium dioxide particles can be sufficiently developed in the fuel oil.

The additive composition according to this embodiment may contain 1 to 5 vol % of the above-mentioned precipitation inhibitor. Usually, the titanium dioxide particles have a comparatively high specific gravity and tend to precipitate. In this embodiment, by adding the precipitation inhibitor to the fuel oil additive, the titanium dioxide particles can be prevented from precipitating not only in the additive composition, but also in the fuel oil to which the additive composition has been added. Thus, when the user adds the additive composition to the fuel oil, the titanium dioxide particles in the additive composition can be added in a comparatively uniform concentration to the fuel oil, and the titanium dioxide particles can be comparatively uniformly dispersed in the fuel oil. Hence the photocatalytic function of the titanium dioxide particles can be more effectively developed.

(Fuel Oil)

The fuel oil according to the embodiment is a fuel oil mixed with the above-described fuel oil additive (including the above-described additive composition). The fuel oil before being mixed with the fuel oil additive is not limited to particular one, and it may be a fuel oil that is popularly commercialized and used. In this embodiment, the fuel oil additive is mixed into the fuel oil in such an amount that the concentration of the titanium dioxide particles in the fuel oil is 0.00001 wt % or more and less than 0.01 wt % (0.1 ppm or more and less than 100 ppm at weight ratio) and more preferably 0.0001 to 0.005 wt % (1 to 50 ppm at weight ratio). The fuel oil mixed with the fuel oil additive as described above can be used by injecting the fuel oil into internal combustion engines.

Example 6

(Fuel Consumption Test 1)

Fuel consumption in the case of adding the fuel oil additive according to the embodiment to gasoline was measured. In Fuel Consumption Test 1, fuel consumptions were measured using two type of gasolines, i.e., (A) gasoline alone, and (B) gasoline prepared by adding 180 ml of the water remover and the fuel oil additive according to the embodiment to 45 L of gasoline such that the concentration of the titanium dioxide in 45 L of the gasoline was 0.003 wt % (30 ppm at weight ratio). The measurement was performed under measurement conditions of driving a vehicle Toyota Porte (model CBA-NNP11) to run 31.8 Km on the highway at 80 Km/h, and attaching Fuel Consumption Manager (FCM-NX1) by TECHTOM Ltd. to OBD (On-board diagnostics) of the vehicle. The following Table 3 lists the measurement results. In Fuel Consumption Test 1, the vehicle was run back and forth between a point A and a point B, and Table 3 indicates the result obtained in a forward route from the point A to the point B, and the result obtained in a forward and return route until reaching the point A after turning back at the point B.

TABLE 3 Type of Fuel Oil Running Average Fuel Total (additives other than gasoline) Distance Consumption Fuel (A) No Additives 16.0 Km 16.66 Km/L 0.9 L (B) Add Water Remover and Fuel Oil 16.0 Km 18.40 Km/L 0.8 L Additive (A) No Additives 31.8 Km 20.71 Km/L 1.5 L (B) Add Water Remover and Fuel Oil 31.8 Km 23.40 Km/L 1.3 L Additive

As seen from Table 3, in the case (B) in which the concentration of the titanium dioxide in 45 L of the gasoline is 0.003 wt % (30 ppm at weight ratio), the fuel consumption is improved by about 10.4% in comparison with the case of using the gasoline alone when the running distance is 16.0 Km. When the running distance is 31.8 Km, the fuel consumption is improved by about 13.0%. The reason why the fuel consumption is worse when the running distance is 16.0 Km than when the running distance is 31.8 Km resides in that, in the total running route, the route from the point A to the point B includes uphill roads over a longer distance (this is similarly applied to Fuel Consumption Test 2).

(Fuel Consumption Test 2)

In Fuel Consumption Test 2, fuel consumptions were measured using three type of gasolines, i.e., (C) gasoline alone, (D) gasoline prepared by adding only 360 ml of the water remover to 45 L of gasoline, and (E) gasoline prepared by adding 360 ml of the water remover and the fuel oil additive according to the embodiment to 45 L of gasoline such that the concentration of the titanium dioxide in 45 L of the gasoline was 0.003 wt % (30 ppm at weight ratio). The measurement was performed under measurement conditions of driving a vehicle SUBARU SAMBAR (model EBD-S331D) to run 35.2 Km on the highway with a vehicle speed held at 80 Km/h, and attaching Fuel Consumption Manager (FCM-NX1) by TECHTOM Ltd. to OBD (On-board diagnostics) of the vehicle. The following Table 4 lists the measurement results. In Fuel Consumption Test 2, as in Fuel Consumption Test 1, the vehicle was run back and forth between a point C and a point D, and Table 4 indicates the result obtained in a forward route from the point C to the point D, and the result obtained in a forward and return route until reaching the point C after turning back at the point D.

TABLE 4 Type of Fuel Oil Running Average Fuel Total (additives other than gasoline) Distance Consumption Fuel (C) No Additives 17.7 Km 19.48 Km/L 0.9 L (D) Add Only Water Remover 17.7 Km 19.71 Km/L 0.9 L (E) Add Water Remover and Fuel Oil 17.7 Km 20.26 Km/L 0.8 L Additives (C) No Additives 35.2 Km 23.39 Km/L 1.5 L (D) Add Only Water Remover 35.2 Km 23.80 Km/L 1.4 L (E) Add Water Remover and Fuel Oil 35.2 Km 24.09 Km/L 1.4 L Additive

As seen from Table 4, in the case (C) in which the concentration of the titanium dioxide in 45 L of the gasoline is 0.003 wt % (30 ppm at weight ratio), the fuel consumption is improved by about 2.8% in comparison with the case of adding only 360 ml of the water remover to 45 L of the gasoline when the running distance is 17.7 Km, and is improved by about 1.2% when the running distance is 35.2 Km.

From Fuel Consumption Tests 1 and 2, it has been proved that the fuel consumption of the fuel oil can be improved by adding, to the fuel oil, the fuel oil additive containing the titanium dioxide particles.

(Emission Measurement Tests for Acid Gases)

Tests were made on gas emissions in the case of adding the fuel oil additive according to the embodiment to gasoline. More specifically, emissions of acid gases were measured using three type of gasolines, i.e., (A) gasoline alone, (B) gasoline prepared by adding only 360 ml of the water remover to 30 L of gasoline, and (C) gasoline prepared by adding 360 ml of the water remover and the fuel oil additive according to the embodiment to 30 L of gasoline such that the concentration of the titanium dioxide in 30 L of the gasoline was 0.003 wt % (30 ppm at weight ratio). In practice, a CO amount and an HC amount in exhaust gas when driving a vehicle to run 2 Km were measured using an exhaust gas measuring device (product name: BANZAI MEXA-324). The following Table 5 lists the measurement results.

TABLE 5 CO amount HC amount (wt %) (ppm) (A) No Additives 0.03 56 (B) Add Only Water Remover 0.04 74 (C) AddWater Remover and Fuel Oil 0.00 7 Additive

As seen from Table 5, in the case (C) in which 360 ml of the water remover and the fuel oil additive according to the embodiment are added to 30 L of gasoline such that the concentration of the titanium dioxide in 30 L of the gasoline is 0.003 wt % (30 ppm at weight ratio), the emissions of the acid gases can be considerably reduced in comparison with the case (B) in which only 360 ml of the water remover is added to 30 L of the gasoline.

(Engine Output Tests)

Tests were made on engine output in the case of adding the fuel oil additive according to the embodiment to gasoline. More specifically, torque and horsepower of an engine were measured for an additive-free fuel oil to which the fuel oil additive according to the embodiment is not added, and for an additive fuel oil to which the fuel oil additive according to the embodiment is added in such an amount that the concentration of the titanium dioxide in 40 L of the gasoline was 0.00125 wt % (12.5 ppm at weight ratio). FIG. 10A is a graph depicting the measurement result of the torque, in which a fat line represents the additive fuel oil and a thin line represents the additive-free fuel oil. FIG. 10B is a graph depicting the measurement result of the horsepower, in which a fat line represents the additive fuel oil and a thin line represents the additive-free fuel oil as in FIG. 10A. Furthermore, a vertical axis of the graph depicted in FIG. 10A denotes torque, and a horizontal axis denotes rotation speed. A vertical axis of the graph depicted in FIG. 10B denotes horsepower, and a horizontal axis denotes rotation speed. The engine used in these tests is a tuning engine.

As seen from FIG. 10A, regardless of the engine rotation speed, the torque is improved in the case of using the additive fuel oil to which the fuel oil additive according to the embodiment is added in comparison with the case of using the additive-free fuel oil to which the fuel oil additive according to the embodiment is not added. When the engine rotation speed is 4500 rpm, for example, the torque obtained with the additive fuel oil is about 16.3 kgf·m, and the torque obtained with the additive-free fuel oil is about 15.8 kgf·m. Thus, the torque obtained with the additive fuel oil is higher by about 0.5 kgf·m than that obtained with the additive-free fuel oil.

Furthermore, as seen from FIG. 10B, regardless of the engine rotation speed, the horsepower is improved in the case of using the additive fuel oil to which the fuel oil additive according to the embodiment is added in comparison with the case of using the additive-free fuel oil to which the fuel oil additive according to the embodiment is not added. When the engine rotation speed is about 6800 rpm, for example, the horsepower obtained with the additive fuel oil is about 139.3 PS, and the horsepower obtained with the additive-free fuel oil is about 137.2 PS. Thus, the horsepower obtained with the additive fuel oil is higher by about 2.1 PS than that obtained with the additive-free fuel oil.

As described above, because of containing the titanium dioxide particles as an active ingredient, the fuel oil additive according to the embodiment can suppress the oil sludge, thereby improving the fuel consumption and reducing the emissions of the acid gases. In particular, since coating treatment is not carried out on the titanium dioxide particles in this embodiment, the photocatalytic function of the titanium dioxide particles can be sufficiently developed. Moreover, in this embodiment, since the titanium dioxide particles are added to the fuel oil in the concentration of 0.00001 wt % or more and less than 0.01 wt %, the photocatalytic function of the titanium dioxide particles can be more efficiently developed, and the oil sludge can be appropriately suppressed. In addition, because of the titanium dioxide particles being nanoparticles with the average particle size of 1 nm to 300 nm, when the fuel oil additive having the photocatalytic function given by the titanium dioxide particles is added to the fuel oil, the effect of making a metal surface closer to a mirror surface and reducing the friction force can be obtained in addition to the photocatalytic function because the titanium dioxide particles polish asperities of the metal surface and infiltrate into the asperities of the metal surface.

Furthermore, in this embodiment, since the liquid fuel oil additive is obtained by mixing the powdery fuel oil additive with another liquid fuel oil additive, the anatase type titanium dioxide particles can be more effectively dispersed into the fuel oil. A fuel oil added with the above liquid fuel oil additive can also be obtained.

The fuel oil additive according to the embodiment can reduce the molecular weight of the fuel oil with the function of the titanium dioxide particles, and can provide the assistant effect of promoting the combustion of the fuel oil. It is also possible to provide the oil-sludge dispersion effect of decomposing and dispersing the oil sludge with the photocatalytic function of the titanium dioxide particles, and the cleaning effect of decomposing carbons, varnishes, and gams. In addition, since combustion of the fuel oil is promoted, the effect of improving the torque and the horsepower of the engine is obtained.

While the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the matters stated in the above embodiments. The above embodiments can be variously modified and improved, and embodiments resulting from modifications and improvements also fall within the technical scope of the present invention.

For instance, while the above embodiments have been described, by way of example, in connection the case of using the anatase type titanium dioxide particles as the titanium dioxide particles having the photocatalytic function, the present invention is not limited to that case, and rutile titanium dioxide particles may be used as the titanium dioxide particles having the photocatalytic function. 

1-28. (canceled)
 29. A method of suppressing oil sludge of a lubricating oil by adding a lubricating oil additive, wherein the lubricating oil additive contains, as an active ingredient, titanium dioxide particles on which coating treatment is not carried out, the titanium dioxide particles are anatase type titanium dioxide particles, and the content of the titanium dioxide particles in lubricating oil is 0.005 wt % or more and less than 0.3 wt %.
 30. The method according to claim 29, wherein the titanium dioxide particles are nanoparticles having an average particle size of 1 nm to 300 nm.
 31. The method according to claim 29, wherein the titanium dioxide particles have the photocatalytic function.
 32. The method according to claim 29, wherein the lubricating oil additive further contains oil.
 33. The method according to claim 32, wherein the lubricating oil additive is given as a composition mixed with oil and containing 0.1 to 5 wt % of the titanium dioxide particles.
 34. The method according to claim 29, the method being effective in additionally improving fuel consumption.
 35. The method according to claim 29, the method being effective in additionally suppressing mechanical vibration.
 36. A method of suppressing oil sludge of a fuel oil by adding a fuel oil additive, wherein the fuel oil additive contains, as an active ingredient, titanium dioxide particles on which coating treatment is not carried out, and the titanium dioxide particles are anatase type titanium dioxide particles.
 37. The method according to claim 36, wherein the fuel oil additive is used in a state of adding 0.00001 wt % or more and less than 0.01 wt % of the titanium dioxide particles to a fuel oil.
 38. The method according to claim 36, wherein the titanium dioxide particles are anatase type titanium dioxide particles.
 39. The method according to claim 36, wherein the titanium dioxide particles are nanoparticles having an average particle size of 1 nm to 300 nm.
 40. The method according to claim 36, wherein the fuel oil additive is given as a composition containing another liquid fuel oil additive.
 41. The method according to claim 36, the method being effective in additionally improving fuel consumption.
 42. The method according to claim 36, the method being effective in additionally reducing emissions of acid gases.
 43. The method according to claim 36, the method being effective in additionally promoting combustion of the fuel oil, cleaning a combustion chamber, or dispersing the oil sludge.
 44. A lubricating oil additive for suppressing oil sludge of a lubricating oil, wherein the lubricating oil additive contains, as an active ingredient, titanium dioxide particles on which coating treatment is not carried out, the titanium dioxide particles are anatase type titanium dioxide particles, and the titanium dioxide particles have the photocatalytic function.
 45. A lubricating oil into which the lubricating oil additive according to claim 44 is mixed.
 46. A grease composition into which the lubricating oil according to claim 45 is mixed.
 47. An fuel oil additive for suppressing oil sludge of a fuel oil, wherein the fuel oil additive contains, as an active ingredient, titanium dioxide particles on which coating treatment is not carried out, the titanium dioxide particles are anatase type titanium dioxide particles, and the titanium dioxide particles have the photocatalytic function.
 48. A fuel oil to which the fuel oil additive according to claim 47 is added. 